Cisco Express Forwarding (CEF)
The two main components of CEF are the forwarding information base (FIB) and the adjacency table. IP routing table is maintained by a router’s control plane. CEF operates in the data plane.

Forwarding Information Base (FIB) — Conceptually similar to a routing table, however, it is structured in a format that is optimized for forwarding. It is even updated when changes occur in the network and there is a one-to-one correlation between FIB entries and routing table entries.

Adjacency Table — Maintains layer 2 next-hop addresses for all FIB entries. Adjacencies can be added manually or discovered through protocols such as ARP or OSPF.

sh ip cef
Shows layer 3 forwarding information. Version is the version of the table and epoch is the number of times the table has been rebuilt.

R1#sh ip cef 10.1.1.1
10.1.1.1/32, version 42, epoch 0, receive

clear ip cef epoch
Here you can see that I rebuild the CEF table and increase the epoch count.